Superheterodyne radio receiving system



Fb, 1 1, 1930. V BEERS v 1,746,576

SUPERHETERODYNE RADIO RECEIVING SYSTEM Filed April 21, 1924 WITNESSES: INVENTOR J X Geo/ye L. Bee/'5 m WM I I ATTORNEY 45 either the Patented Feb. 11, 1930 Y UNITED STATES PATENT oFFIcE i GEORGE L. IBEERS, OF WILKINSIBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA SUPEBHETERODYNE RADIO RECEIVING SYSTEM a lication filed April 21-,

My invention relates to radio receiving apparatus and particularly to radio receiving apparatus of'the super-heterodyne type.

An object of my-invention is to produce 6 a radio receiving system of high selectivity and sensitivity having a single tuning control means.

Another object of my invention is to produce a super-heterodyne type of radio receiv- 6 In the prior art of the reception of radio frequency signals, it has been customary to use a radio receiving system comprising an adjustablytuned radio receptor circuit,- an adjustable oscillation generator cooperating therewith to produce, a heterodyned signal,

an amplifier means adapted to amplify the heterodyned signal, anda detector to convert the heterodyned signal to an audio-frequency signal. This construction required a plurality of adjustably tuned means which could not readily be actuated from a single lever. In the operation of such a system, difliculty is experiencedby the operator in adjusting the two control devices to properoperating points, since they must be synchronized with great care in changing from one wave length to another.

The super-heterodyne receiving apparatus of the prior art is convenient because of the 0 high degree of amplification which it applies to faint signals. When stronger signals are received on the aerial, however, the same amplification may produce excessively loud signals in the receivers, which may overload last amplifier tube or the signal receivers.

My invention comprises means whereby a super-heterodyne receiving apparatus may be tuned by a single control means. I accom- '50 plish this result by making the aerial circuit 1924. Serial No. 707,833.

non-resonant to the frequencies which are desired, but responsive to all of them. All

frequencies are thus received and heterodyned by the oscillator to.a variety of lower frequencies, all of which-change with the frequency of the oscillator. The heterodyned frequency which corresponds to the frequency to which the amplifier system is resonant, is then selected, amplified, and detected by the successively following elements of the system. By this means a changein the frequency of the heterodyne driver, changes the frequency to which the responds.

My invention further comprises means for system, as a whole,

controlling the volume of the amplified anddetected signal, through changes in the close- 'ness of coupling between an aperiodic 'antenna circuit and an aperiodicamplifier cirfrequencies by any convenient means, such as byproviding a sufliciently high resistance in theaerial to broaden the natural resonant period to the desired extent, or, by making the aerial resonant to a frequency higher than that which it is desired to receive.

Inductively coupled to the inductance 2 is an inductance 1 connected between the grid andthe cathode'of an amplifier triode 5. The inductive coupling between the coils 2 and 4 is made adjustable. This amplifier triode 5 is supplied with the required additional operating energy from the batteries A and B. The triode 5 is adapted to function as an aperiodic amplifier at all of the desired signal frequencies. The circuits thereof are made aperiodic by means similar to those for the receptor circuit. The anode circuit of the triode 5 is capacitively coupled by a condenser 7 to the grid of a triode 8 which is adapted to function as a heterodyning oscillator. The anode circuit of the triode 8 contains an inductance 9. The grid circuit of the triode 8 contains. an inductance 11 shunted by a condenser 12. The inductance 11 and the inductance 9 are in inductive relation whereby an energy feed back from the anode circuit to the grid circuit is obtained and the device set into self-oscillation at a frequency determined by the setting of the condenser 12.

A second inductance 14 is connected in the anode circuit of the triode 8 and is in inductive relation to the inductance 15 which is connected between the cathode and the grid of an amplifier triode 16. The anode v circuit of, the triode 16 contains an inductance 17 in inductive relation to an inductance 18. The inductance 18 is connected between the cathode and the grid of a detector triode 19', through a grid leak and grid condenser combination 21. The anode circuit of the triode 19 is connected through the primary 22 of an amplifier transformer 23, the secondary 24 of which is connected between the cathode and the grid of a triode 25. The anode circuit of the triode 25 contains a signal receiver device 26. The triodes 5, 8, 16, 19 and 25 are supplied with current from the batteries A and B by appropriate connections as shown in the drawing.

In the operation of my device, signals incident upon the antenna 1 will cause a current to flow through the radio receptor circuit comprising the aerial 1, the inductance 2 and the ground connection 3. Energy from these signals is transferred through the induc-' tance 4 to the triode 5, amplified thereby and impressed throu h the condenser 7 upon the grid of the trio e 8. The triode 8 is maintained in oscillation at a radio frequency. This oscillation will generate beats when combined with the signal energy which is re,-

ceived by aerial 1, when it is amplified by the triode 5 and impressed upon the grid of the triode 8. r

The grid circuit of the triode 16 is made resonant to a predetermined frequency, and if the beat frequency produced between the oscillations of triode 5 and some signal incident upon antenna 1 is the frequency to which the grid circuit of the triode 16 is re- .sonant, this beat note is resolved by the triode 8 and transferred through the inductances 14 and 15 to the triode 16, by which it is amplified, and transferred through the inductances 17 and 18 to the detector 19. It, is there detected, transferred at audio frequency byfthe transformer 23 to the triode 25, amplified therein and caused to energize a signal receiver 26.

, Signals may be incident upon aerial 1 at a frequency other than the one which, when allowed to generate a beat frequency with nance of the grid circuit of the triode 16 to I such frequency, they are not transferred further and, therefore, do not appear in the signal reproducer 26. When it is desired to receive signals at that different frequency, the frequency of oscillation of the triode 8 is changed by means of a change in the adjustment of the condenser 12 to produce an oscillation frequency which will produce beats with the desired signal at the frequency to which the grid circuit of the triode 16 is resonant.

When faint signals are being received, the coupling between the coil 2 and the coil 4: may be made as close as possible, whereupon a maximum amount of signal energy is transferred to the triode 5, and maximum signal volume delivered by the receiver 26. When,

however, stronger signals are received, and too great signal volume is delivered by the receiver 26, the coupling between the coils 2 and 4 may be reduced, whereupon, because of the aperiodic nature of both coils, less signal energy is transferred to the triode 5 and less signal volume is delivered from the receiver 26. 7

By this means, I am enabled to produce a super-h'eterodyne receiving system having high selectivity, the tuning of which is sub.- ject tov control by a single adjustment, and

a system in which the amplified signal vol ume is subject to control by coupling between an aerial coil and an amplifier coil.

While I have shown only one embodiment of my invention in the accompanying drawing, it is capable of various changes and modifications withoutdeparting from the spirit thereof,and itis desired, therefore, that only such limitations shall be imposed thereon as are indicated in the prior art or in the appended claims.

I claim as my invention: I 1. A radio receiving system comprising m combination an aperiodic radio receptor, an

aperiodic amplifier means connected thereto,

a heterodyne generator cooperating therewith, a selective amplifying means supplied therefrom, and a detector connected thereto,

receiving system may be independently accomplished, each by a single adjustment. 3. A radio receiving systemincluding an antenna circuit havin a natural frequency 5 outside of the band of requencies it is desired to receive, an amplifier having untuned input and output circuits, means for coupling said input circuit to said antenna circuit, and a, second amplifier having an input circuit coupled to said untuned output circuit, theinput circuit ofsaid amplifier including a single adjustable tuning element, whereby the calibration of said tuning element is independent of changes in the constants of an antenna connected to said antenna circuit.

4. A radio receiving system including an antenna circuit having a natural frequency outside of the band of frequencies it is desired to receive, an amplifier having untuned input and output circuits, means for variably coupling said input circuit to said antenna,

' and a second. amplifier having an input circuit coupled. to said untuned output circuit, the input circuit of said second amplifier ineluding a single adjustable tuning element.

In testimony whereof, I have hereunto subscribed my name this 16th day of April, 1924.

' GEORGE L. BEERS. 

